The 49ers insisted they were Friday as they bundled up and headed off for a game expected rank among the coldest in NFL history. There NFC wild-card game against the Green Bay Packers will be about 2 degrees at kickoff, with a wind-chill factor of minus-20, making things about as frosty as a Jim Harbaugh press conference.

The National Weather Service ventures that by the fourth quarter it will be minus-7 with a wind chill approaching minus-30. The Packers plan to pass out 70,000 hand-warming packets for fans to slip inside the gloves or boots. The team will also provide free coffee and hot chocolate.

How cold is it? Justin Smith, the 49ers’ famously grizzly defensive tackle, was considering the possibility of wearing long sleeves.

“There’s no advantage to not wearing them. It’s not like you’re not going to scare the opponent,” Smith reasoned. “They might call you a dumb-ass.”

Then again, 49ers quarterback Colin Kaepernick said he had no plans to wear a glove on his throwing hand. Offensive lineman Alex Boone plans to go bare-armed, something his family thinks is nuts.

Boone recounted that story for KNBR on Friday and said that when his mom and grandma objected, he quipped: “Leave me alone I’m going to play football. I don’t tell you what to wear to work.”

Indeed, several 49ers said this week that the key to battling the elements is not even think about them — to weatherproof your brain.

“Wet. Cold. Snowy. We have to go play football,” linebacker Patrick Willis said.

“You have to block it out,” Kaepernick said.

“Make it a normal game the best you can,” defensive coordinator Vic Fangio said.

Privately, however, even players might admit to making a few concessions to the temperatures. Former linebacker Brendon Ayanbadejo, a Santa Cruz native who played 10 of his 13 professional seasons in cold-weather cities, wrote a lengthy first-person account for foxsports.com this week. His advice included spraying his hands with Tinactin (the athlete’s foot remedy) and wearing sterile rubber gloves underneath his football gloves.

One other tip: Keep moving.

Harbaugh agrees with that one. The onetime quarterback got his fill of snowy games as a college star at Michigan and later for the Chicago Bears from 1987-93.

Harbaugh spent most of the week dismissing weather questions, but on Friday he delivered this scientific assurance of why his players would be fine: “The heart rate ramps up, the hot blood races to the arteries, to the vessels, to the capillaries, and there distributed to the fingers and the toes. In an athlete, the age and the health of these guys, that hot blood will be racing around.”

Some guys, though, really will have to think about the weather. They’re called coordinators. Greg Roman, who calls plays for the 49ers offense, acknowledged that his game plan will be affected by the forecast.

Besides being cold and windy, Roman said, the footing could be treacherous. That means he’ll have to keep an eye on which parts of the field are holding up best, figuring the play call might vary from yard line to yard line.

There’s also an added degree of difficulty for the quarterback, who might feel as if he’s chucking a shot put.

“The ball is going to be harder and that’s really the No. 1 obstacle,” Roman said. “Obviously, depending on the wind, you’ve got to try and pierce the wind with your throw. But, it’s more about the ball and grip.”

Fangio, too, said that the ground will be a bigger factor than the air. “It all depends upon what the footing’s like. It could be just a normal game that’s played at a little slower pace,” the defensive coordinator said. “Or it could be where there’s a lot of slipping and sliding going on then you have to adjust a little bit.”

Conventional wisdom is that snowy conditions make a better environment for the running game, which would favor the 49ers. San Francisco ranked third in the NFL in rushing yards per game (136.6) and rushing attempts per game (31.6).

The Packers had a top-10 running game, too, but their offense is built around quarterback Aaron Rodgers.

Advantage 49ers? Not so fast, said John Madden. The Hall of Fame former Raiders coach said on his KCBS podcast that “the ice and the snow favors the passing game because it’s tougher on the defensive backs and the pass rush. The rain, as long as they keep the footballs dry, it’s the same thing.”

Madden also said Green Bay players have more experience in such blustery conditions, which means they have learned how to cope.

“No one likes cold weather. They used to say that about Brett Favre, that he likes cold weather,” Madden told KCBS. “He used to tell me, ‘I hate cold weather just like everyone else does. I’ve just learned to play in it.’”‰”

The 49ers, too, have players who are old hands at cold hands. Receiver Anquan Boldin, who played for the Baltimore Ravens last year, recalled the game-time temperature of 13 degrees for a playoff game at Denver. Boldin had six catches for 71 yards.

And then there’s kicker Phil Dawson, who spent 14 years in Cleveland and learned there’s no business like snow business.

“I try to forget those, the really cold ones,” Dawson said Friday. “But I’ve had a few below-zero wind chills, way down there. They’re tough days, but it’s where that mental toughness comes in.

“Literally, snapping, catching, throwing, ball-handling, all these types of things become a huge issue. The team that handles the conditions better will win.”